This regime began to draw public attention in August 2012 through the documentary 'Horizon' presented by British physician and journalist Dr Michael Mosley, but the diet lacks substantial medical evidence to establish it as a safe, healthy weight-loss method.

"It's the next big thing," said Dr Muireann Cullen, manager of the Nutrition and Health Foundation. "We've had Atkins Diet, the Maple Syrup Diet and the Cabbage Soup Diet. While it does look promising, more research needs to be done."

Claimed benefits include a longer life expectancy, weight loss, lower cholesterol and glucose levels, and protection against Alzheimer's disease.

However, Dr Cullen cautions: "Much of the research for the diet has been based on animal trials rather than clinical studies on humans. The effect of the diet on degenerative diseases has not been proven at this moment in time. But it will be interesting to see future research in the area."

The popularity of the diet has resulted in a number of best-selling books in Ireland but it poses many concerns for nutritionists.

Reducing the intake of micronutrients such as iron or calcium could present problems for those already low on these vital nutrients.

"Most Irish adults have an insufficient calcium intake with 1 in 2 women and 1 in 5 men expected to develop osteoporosis in their lifetime. Furthermore, reducing iron intake could present a problem for women as iron levels already decrease during menstruation," said Dr Cullen.

"Even though you are on a diet, it is still necessary to exercise. If you don't have the energy to exercise then that's a problem."

She finds many dieters following the 5:2 pattern tend not only to overeat on the days they are not fasting, but also find sustaining the diet extremely difficult.

Dr Cullen advised that if a person wishes to lose weight to focus on "tried and tested methods" rather than fad diets. She recommends the use of the food pyramid as a guide and a simple four-point plan:

Get adequate exercise.

Pay attention to portion sizes.

Watch the frequency of your meals.

Look at how you cook your foods.

Online Editors

Your Comments

COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? customercare@belfasttelegraph.co.uk